Sign forming apparatus, method and die for use therein

ABSTRACT

A die heating station is supported for movement between a ready position and a cutting position. In the cutting position a die is brought into contact with a sheet of thermoplastic material supported on a carrier having a suitable cutting pad against which the die can bear to cut a letter of a word. A die cooling station receives each die after the cutting operation and cools it to an operator-handleable temperature. A particular die structure is used which facilitates rapid heating and cooling of the die while retaining the necessary thermal properties for cutting thermoplastic sheet material. A procedure and guide is provided for accurately spacing adjacent letters of the word being cut.

111 3,826,167 July 30, 1974 SIGN FORMING APPARATUS, METHOD AND DIE FOR USE THEREIN [75] Y Inventors: Pierre A. Pelet, Mill Valley; Bernard Bouyssounouse, Palo Alto; Fritz Haas, Concord, all of Calif.

[73] Assignee: PST Company, Sausalito, Calif.

[22] Filed: May 19, 1972 [211 App]. No.: 255,243

[52] US. Cl 83/171, 83/8, 83/522 [51] int. Cl B26d 7/10 [58] Field of Search 83/171, 8,684, 522; l0l/8l1 [56] References Cited UNITED STATES PATENTS 3,l6l.554 12/1964 Blackford 83/171 X 3.465.627 7/1969 Vigneault 83/684 X Primary ExaminerAndrew R. Juhasz Assistant Examiner-Leon Gilden Attorney, Agent, or Firm-Roland l. Griffin [57] ABSTRACT A die heating station is supported for movement between a ready position and a cutting position. In the cutting position a die is brought into contact with a sheet of thermoplastic material supported on a carrier having a suitable cutting pad against which the die can bear to cut a letter of a word. A die cooling station receives each die after the cutting operation and cools it to an operator-handleable temperature. A particular die structure is used which facilitates rapid heating and cooling of the die while retaining the necessary thermal properties for cutting thermoplastic sheet material. A procedure and guide is provided for accurately spacing adjacent letters of the word being cut.

25 Claims, 9 Drawing Figures SIGN FORMING APPARATUS, METHOD 7 AND DIE son USE THEREIN BACKGROUND OF THE INVENTION of characters such as words. It also relates to a particular die construction and to fonts of such dies for use in the sign making apparatus. I

Heretofore, several systems for so-called instant sign making have been developed. In one system precut letters pre-mountedon a release sheet are selected and are arranged into an appropriate word or other pattern at the time of making up a sign. This requires a large inventory of pre-cut individual letters in various fonts and sizes as well as in different materials.

In another system dies are individually used to cold cut letters or characters at the time the sign is to be made up. Such dies must be extremely strong and must have a relatively sharp cutting edge which limits their useful life. In addition, the coated tapes or materials that can be fabricated into signs using cold die cutting are somewhat limited.

Hot die cutting is known and is found to assure uniformity and versatility not possible in cold die cutting. Normally, a press is equipped with a die heater maintained at a temperature adequate to melt the sheet material from which the characters are to be formed. Such machines, however, have been developed for mass producing large quantities of the same character, as for use in the first system mentioned above, and have not lent themselves to use for properly obtaining pre-spaced, serially formed sets of characters forming entire words or lines. There is, therefore, a need for new and improved sign making apparatus and improved dies for use therein.

SUMMARY OF THE INVENTION It is a general object of the present invention to provide new sign forming apparatus and dies for use therein which will overcome the above-mentioned limitations and which will provide the advantages of hot die cutting in a simple easy-to-operate arrangement adapted for use on conventionally available thermoplastic sheet material.

A further general object of the invention is to provide new sign making apparatus and dies of the above character in which entire words and phrases can be cut into thermoplastic sheet material with the letters and characters in properly spaced positions, can then be transferred together as a unit to an application substrate while preserving the spacing thereof, and can subsequently be applied to an object to form a high quality sign of hand painted appearance at a fraction of the presentcost for a hand painted sign and without the need for skilled labor.

Another object of the invention is to provide sign forming apparatus of the above character which is simple to construct and reliable in operation and which permits die insertion and removal therefrom at operator handleable temperatures.

Another object of the invention is to provide sign forming apparatus of the above character which is readily adapted to use dies of any font design andwhich requires only an inventory of basic thermoplastic material such as a variety of rolls of thermoplastic tape in differing appearance or color.

Another object of the invention is to provide a sign forming apparatus and dies of the above character in which the standard spacing of the characters is derivable from indicia carried on the dies and read by the operator in using the apparatus, but in which the spacing of the characters may also be varied for certain combinations to assume a more eye-pleasing effect.

Another object of the invention is to provide sign forming apparatus and dies of the above character in which the dies are designed for ease of manufacture and rapid heating and cooling.

In general, the sign forming apparatus of the present invention includes a framework defining a carrier plane for receiving a sheet of thermoplastic material and for supporting same in a cutting position over a platen. A die heating station is mounted in the framework for movement between a ready position and a cutting position and is provided with a die receiving and advancing mechanism for sliding a die into contact with a heated plate. A die cooling station is also mounted in the framework and is provided with a die advancing mechanism that is aligned with the die receiving and advancing mechanism of the die heating station when the latter is returned to the ready position so that dies may be sequentially inserted into the die heating station, brought to the cutting position, returned to the ready position, and ejected through the die cooling station. The insertion of each die into the die heating station and its subsequent removal from the die cooling station is performed by hand operation and by selection of the operator.

Each die is constructed of high thermal-conductivity, low heat-capacity material, such as an aluminum or magnesium alloy, and has a relatively thin planar back on which is integrally formed a raised bulb portion crowned with a bead tapering to a cutting edge outlining a character. The bulb portion has sufficient mass to serve as a heat sink for the cutting bead so the latter does not become excessively cooled as it is brought into contact with the material being cut.

The foregoing sign forming apparatus is characterized by the use of a large capacity heated plate at the die heating station to provide substantial stored thermal energy. Each die, being made up of a thin section of low heat-capacity material, has low thermal inertia. Thus, the dies being advanced through the sign forming apparatus are rapidly heated from contact with the heated plate without causing any substantial change in the temperature of the heated plate and are readily cooled before being removed by the operator.

In use, an operator selects a die and inserts it into the die heating station after having first removed any die located in the die cooling station and after having remotely transferred any die from the die heating station to the die cooling station (all of this being done while the die heating station is in the ready position). In this way the last letter which has been cut is located in the die cooling station and the letter to be cut is located in the die heating station. The operator then advances the thermoplastic sheet material a distance equalling the sum of the half widths and spaces for the respective dies in the die heating and cooling stations, if necessary, and then remotely manipulates the die heating station to the cutting position bringing the die therein into thermo-cutting relationship with the thermoplastic sheet. The die heating station is then returned to the ready position, and the foregoing steps are repeated until the necessary sign is completed.

These and other objects and features of the invention will become apparent from the following description and claims when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective exploded view, partially in schematic form and with portions broken away or removed for clarity, of sign forming apparatus constructed in accordance with the preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of the sign forming apparatus taken along the line 22 of FIG. 1.

FIG. 3 is a cross-sectional view of the sign forming apparatus taken along the line 33 of FIG. 2.

FIG. 4 is a cross-sectional view of the sign forming apparatus taken along the line 4-4 of FIG. 1.

FIG. 5 is a top plan view of a position indicating detent mechanism taken generally from the plane defined by the line 5-5 of FIG. 2.

FIG. 6 is a front plan view of a die that may be used in the sign forming apparatus of FIG. 1 and that is constructed in accordance with the preferred embodiment of the present invention.

FIG. 7 is a rear plan view of the die of FIG. 6.

FIG. 8 is a cross-sectional view of the die taken along the line 8-8 of FIG. 7.

FIG. 9 is a detailed cross-sectional view of a die as the same is brought into the operative cutting position in the sign forming apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the overall concept of the sign forming apparatus of the present invention is shown and generally includes a die heating station 12 having guides on its lower side for slidably receiving a die 14 and having a gear driven advancing mechanism 16 for advancing the die into a centrally disposed position within the heating station and into contact with the lower face of a heating plate 18. The die heating station is carried in a framework provided with suitable guides and a mechanism 19 for raising the die heating station from a lower cutting position to an upper ready position. In the upper ready position, a die carried in the die heating station is aligned with a die cooling station 20 so that it can be ejected from the die heating station directly into the die cooling station by advancing mechanism l6 and another advancing mechanism 22 associated with the die cooling station. A roll of thermoplastic sheet material is serially advanced together with the insertion and removal of a respective set of dies to and from the apparatus after each letter is cut.

Referring more particularly to FIGS. 1 through 3, the apparatus of the present invention is generally contained within a framework which also serves as a protective housing for the various components. The framework generally consists of a pair of side plates 30 and 32 held in fixed positions in spaced parallel planes with respect to each other by a base plate 33 and by spacing and support rods 34. The base plate consists of a single unitary section having a flat upper surface and includes an interchangeable resilient cutting pad or platen 37 made of silicone rubber, for example, and located in a centrally disposed area where the cutting pad serves as a backing against which the die of the present invention operates, as will be hereinafter described. At one end of the base of the framework a pair of spaced roll support rods 38 and 40 serve to support a roll 42 of thermoplastic sheet material in the form of a strip of uniform width.

A spacing scale 43 past which the thermoplastic strip passes before proceeding to the platen 37 is marked on one of a pair of rails 44 and 45 overlapping the thermoplastic strip from each side of the base of the framework and is provided for the operators use in the spacing of letters. Rails 44 and 45 also serve to align the thermoplastic strip into a feed position with respect to the platen 37 and the base of the framework. Spacing scale 43 is linear and consists of numbered tens units together with subdivision marks dividing each tens unit into units. The thermoplastic strip is passed over the platen 37 and under a hold-down clamp 46 consisting of a J-shaped plate 46a articulated from a pivot shaft 46b mounted between the side plates 30 and 32 and having a lower rounded edge lying in engagement with the upper surface of the thermoplastic strip. Thus, a strip 47 of thermoplastic material may be drawn over the platen 37 by being pushed into the sign forming apparatus from the roll 42 and by being withdrawn at the other end by the operator.

The thermoplastic sheet 47 used in the sign forming apparatus of the present invention can be any of various kinds in which a thermoplastic layer 47a having a pressure-sensitive adhesive backing is bonded to a suitable heat-resistant release backing 47b (see FIG. 9). By way of example, a 2 mil layer of vinyl plastic with an adhesive coating on its back laid over a silicone coated paper release liner, such as is sold by the 3M Corporation under the trade designation Scotchcal (trademark) or Scotchlite (trademark) is satisfactory.

The side plates 30 and 32 extend upwardly on each side of the platen 37 and are held in spaced relation by upper and lower guide shafts 48 and 50 which are arranged in spaced vertical relation to each other above the platen. Guide shafts 48 and 50 carry spaced retaining ring sets 52-53 and 54-55, respectively, in grooves formed on the shafts. These retaining ring sets serve as lateral guides for restraining lateral movement of die heating station 12. The upper shaft 48 also serves as a reaction shaft for moving die heating station 12 and for that purpose is provided with an eccentrically mounted cam 58 having a circular shape and having a handle 110 for rotating the cam such that the lobe 60 of the cam moves from an uppermost position shown in FIGS. 1 and 2 to a lowermost position in which the lobe of the cam is directed vertically downward.

As shown particularly in FIGS. 1 and 2, the die heating station includes a heating plate 62 having an aperture 64 therethrough for receiving an electrical resistance heater 66 which is connected to a suitable electrical supply through a thermostat (not shown) mounted on the heating plate to stabilize the temperature of the heating plate within a predetermined range. The heating plate 62 has a flat lower surface and serves to distribute heat from the heater 66 uniformly to that surface. If desired, a visual reading thermometer (not shown) may also be disposed on the heating plate 62 to give the operator an indication when the heating plate is sufficiently hot. The lower surface of the heating plate 62 is bounded back and front by side rails 68 and depending downwardly and defining a carrier plane through which a die 14 can be passed. The upper surface of the heating plate is provided with upwardly extending front and rear brackets 72 and 74 for supporting a gear drive consisting of a centrally located shaft 76 supported by bearings 78 and 80 mounted on these brackets and carrying drive gears 82 and 84 at each end of the shaft 76.

First and second sets of resilient rollers 86a and 86b are mounted on bearings at laterally spaced positions along the path of die movement and may, for example, be carried at one end of shafts extending through the downwardly depending side rails 68 and 70. First and second sets of driven gears 90a and 90b are mounted at the other end of these shafts. The spacing between the lower surface of heating plate 62 and the rim of resilient rollers 86a and 86b is made slightly less than the thickness of the die 14 to be carried so the die can be transferred through the die heating station by the action of these rollers, when driven, with the rear surface of the die in sliding contact with the heating plate 62. First and second sets of idler gears 94a and 94b are mounted on the gear support brackets 72 and 74 in driven engagement with drive gears 82 and 84 and in driving engagement with driven gears 90a and 90b. in this way rotation of drive gears 82 and 84 by the operators manipulation of knob 98 serves to drive both sets of idler gears 94a and 94b in a similar sense and likewise to drive both sets of driven gears 90a and 90b together with their associated rollers 86a and 86b such that a die 14 can be carried through the die heating station, can be remotely adjusted to any position therein, and can be ejected if desired.

Referring to FIG. 5, there is shown a detent mechanism consisting of an L-shaped lever 100 carrying a bearing mounted roller 102 at one end and pivoted at an intermediate point 104. The lever 100 is biased by a spring 106 attached between the other end of the lever and the die heating station so as to pivot the roller 102 slightly into the path of the die 14. Each die is provided with a notch 108 disposed along the rear edge of the die so an operator can feel when the die is centrally disposed in the die heating station due to the change in resistance of movement caused by the roller 102 entering the notch 108.

As shown in FIGS. 1 through 3, a mechanism is provided for moving the die heating station 12 between and for supporting the same in a ready position (see FIG. 1) spaced away from the platen 37 and in a lowered cutting position at which the die 14 is impressed into contact with the thermoplastic sheet material to cut the same by heat melting. This mechanism includes the cam 58 and handle 110 together with a cam plate assembly 112. The cam plate assembly 112 consists of a pair of oppositely arranged cam plates 114 and 116 mounted, as with screws, on the upper surface of the heating plate 62, extending upwardly in spaced parallel planes, and terminating at their upperends by being bent so as to overlie the uppermost surface 118 of the cam 58 from the front and rear sides thereof. .The portions of the cam plates 114 and 116 which overlie the cam 58 serve to support the entire die heating station 12 on the upper surface of the cam and, hence, on the reaction shaft 48. The cam plate assembly is constrained to follow a linear path of motion by guide slots 120a, 120b, 122a, and 12211 in the cam plates 114 and 116 through which the respective shafts 48 and 50 extend. The cam plate assembly is also constrained to remain centrally disposed by the rings 52-55 previously described. Thus, the die heating station is free to move up and down following the position of the upper surface of cam 58. A cam follower 120 is mounted immediately below the cam 58 and consists of a cylindrical roller 122 mounted on a shaft 124 having an axis slightly displaced from the roller axis so that by using a knob 126 attached to shaft 124 an eccentric fine ad- 10 justment may be made to determine the precise limit of the stroke of the die heating station 12 as the same is moved downwardly toward engagement with the thermoplastic material and pressed toward the platen 37. A screw 128 serves to lock the knob 126 in place once the desired fine adjustment is achieved. Initially, as handle 110 is rotated, the die heating station 12 moves downwardly under gravity while resting on cam 58 until a die 14 supported by the die heating station comes into resting contact with the upper surface of the thermoplastic material. Thereafter, further movement of the handle 110 causes the lowermost surface of the cam 58 (then on lobe 60 of the cam) to bear against the roller 122 and thereby drive the die heating station 12 downwardly into precisely spaced position with respect to the platen 37.

A mechanism is provided for clamping the thermoplastic strip 47 into fixed position in response to initial movement of the die heating station towardsthe platen 37. This mechanism includes a pair of clamp rails 130 and 132 having portions overlying each side of the platen 37 and the thermoplastic strip 47 supported thereon. Clamp rails 130 and 132 are pivoted at positions 130a and 132a remote from the platen 37 and are biased toward the platen by suitable springs 134 and 136. The ends of the clamp rails 130 and 132 are further provided with upstanding end portions 138 terminating in rollers 140 so positioned that when the clamp rails are released into clamping position the rollers 140 lie in the upward path of projections 142 formed at the ends of the heating plate assembly and at a level such that return of the die heating station 12 to its uppermost position causes the projections 142 to engage the rollers 140 and thereby release the clamp rails by pushing the rollers 140 outwardly and lifting the clamp rails off the platen 37.

Referring to FIGS. 1 and 4, a die cooling station is mounted in the framework on brackets 152 and 154 and generally consists of a cooling plate having a lower surface 156 of substantially the same area as the die 14 to be passed therethrough and having a plurality of integrally attached fins 158. Such structures are well known in the transistor cooling art as heat sinks and, in fact, a large transistor heat sink was utilized as the cooling plate in one form of the present invention. A suitable fan 160 blows or draws ambient air past the cooling fins 158. The cooling plate mounting brackets 152 and 154 are positioned so that the bottom surface of the cooling plate is aligned to receive a die from the die heating station 12 when the die heating station is in its raised ready position.

A mechanism is provided for advancing the die 14 through the die cooling station and consists of three sets of resilientlyfaced rollers 161, 162, and 163 supported on shafts 164 which are mounted for rotation at spaced-apart positions along the path of the die. These resiliently-faced rollers extend upwardly to support the die 14 in sliding contact with the lower surface 156 of the cooling plate. The roller shaft 164 nearest the die heating station 12 is provided with a knob 168 for turning that shaft to thereby facilitate transfer of a die from the die heating station to the die cooling station and to also permit partial ejection of a die from the die cooling station. The end of the die cooling station from which the die is ejected is conveniently provided with a tearoff bar against which the thermoplastic strip 47 is severed after an appropriate segment of a sign has been completed.

Referring now to FlGS. 6 through 9, a suitable font of dies 14 is provided and includes an alphabet and numeral set as well as any other characters that may be required for sign making. Such a font may have any particular design. Each die 14 is formed on a flat plate 170 of relatively thin cross section. A raised bulb portion 172 is disposed on the plate 170 and integrally joined thereto, the raised bulb portion conforming generally to the outline of the character to be represented on the die. A bead 174 is formed on the bulb portion 172 and converges into a broad cutting edge. The head 174 and bulb portion 172 are integrally formed together with the plate 170 such as by casting them in a mold. Generally, the plate 170 is made of a relatively high thermal-conductivity, low heat-capacity material which facilitates the rapid heating and cooling of the die. Many aluminum and magnesium alloys are satisfactory for this purpose, such as 380 AL-Si. The bulb portion 172 is generally as thick and may be slightly thicker than the plate 170 itself and serves as a heat sink for supplying the bead 174 with adequate heat so that as the bead is pressed into contact with the ther moplastic material the bead will rapidly cut through the thermoplastic material without being unduly cooled. As an example, a die 14 for a inch letter has been utilized in which the plate 170 was 0.075 inches thick while the bulb portion 172 was approximately 0.100 inches in depth and had a diameter of approximately three-eighths of an inch. The bead 174 forming the cutting edge had a depth of 0.020 inches and had a subtended angle of convergence toward the tip of 106 with a tip radius of 0.010 inches.

Each of the dies 14 is characterized by being as thin as possible, consistent with reasonable rigidity requirements, to thereby reduce the metal mass and thermal inertia so that rapid heating and cooling can be achieved. In addition, the dimensions of the bulb portion 172 and bead 174 are chosen so that due to the relatively large mass of the bulb portion and its ability to provide adequate heat to the head a melting action is achieved rather than a mechanical cutting action.

Each of the dies 14 is also provided with a suitable indicia 176 thereon for indicating its normal spacing relative to other characters. While the spacing may vary for particular combinations, it nevertheless is sufficiently uniform that such indicia can be made to indicate to a sufficient degree of accuracy a generally suitable spacing. Particular combinations may be spaced by eye or by an auxiliary device if desired.

As shown in FIGS. 1, 2, and 4, apparatus is provided for reading the spacing indicia from each die 14 positioned in the sign forming machine to supply spacing indicia readings as required for both the last die used, which is then in the die cooling station 150, as well as the die in the die heating station 12. This apparatus includes a light 180 and a cover 182 mounted on the rear side plate 32 to direct light inwardly across a face of the die at the die heating station. It also includes a second light 184 and a cover 186 mounted on the rear side plate 32 to direct light across a face of the die in the die cooling station. At the front of the sign forming machine aperatures are provided together with mirrors 188 and 190 for permitting the operator to look upwardly onto the illuminated faces of the dies at the die heating station and the die cooling station. The numbers used for indicating spacing correspond with the spacing scale 43 engraved on feed rail 45. Each of the spacing numbers indicates the half width of its respective character plus the half width of the appropriate space between that character and its neighbor. The total half width and half space of each character is added to that of the adjacent character to provide the total center-to-center spacing of that combination. This is used as the distance which the thermoplastic strip 47 should be advanced to properly space characters.

The operation of the device ,will now be described and reviewed in detail with particular reference to FIGS. 1, 2, and 4. After the sign forming apparatus is turned on and the correct heat range is obtained, a strip 47-of thermoplastic sheet material is inserted between the feed rails 44 and 45 at the right side and is fed an appropriate distance through the sign forming apparatus and beyond the platen 37. The first character of a word to be imprinted is selected from a font of dies 14 of the desired size and style. That particular die 14 is then inserted into the die heating station 12 immediately under the heated plate 62, an arrow 192 on the rear face of the die being disposed toward the operator. The die transfer knob 98 is rotated until the die 14 is centered under the heated plate 62 as can be felt by the action of the detent mechanism of FIG. 5. A reference mark should then be drawn on the thermoplastic strip 47 at zero on the spacing scale 43.

The interval of time from insertion of the die 14 until it is sufficiently hot may be measured with a timer (not shown). After this time lapse, which is on the order of about 15 seconds, the handle 1 10 is swung from the position shown in FIG. 1 through 180 degrees to cause the lobe of cam 58 to rotate and to bear down upon the roller 122, thereby lowering the die 14 into pressed contact with the thermoplastic strip 47. The manner in which thermal cutting action is effected is shown in detail in FIG. 9. The level of the die 14 in the cutting position is adjusted by rotating knob 126 until the cutting bead 174 of the die penetrates the thermoplastic material 47a and presses slightly into the release backing 47b such that the same is deformed slightly into the resilient platen 37. As the cutting action takes place, the thermoplastic material 47a is melted and forms a small bead of thermoplastic material on each side of the cutting line. The depth of the cutting bead 174 on the die 14 is at least sufficient to accommodate this raised edge or bead of excess thermoplastic material and to provide adequate relief therefor. It has been found that 2 mil vinyl tape, for example, can be melted and cut in about 5 seconds using the above procedure, thereby permitting the handle to be returned almost immediately.

The die positioning knob 98 of the die heating station 12 is then advanced to send the die 14 to the die cooling station where it is advanced by knob 168 and rollers 161. The next die 14 required to form the word is then inserted into the die heating station 12 and aligned. At this time both the previous half width spacingand the present half width spacing appear in the respective mirrors 190 and 188. The sum of these half width spacings becomes the desired inter-letter spacing. The thermo-plastic strip 47 is then advanced the distance of that sum as by marking the thermoplastic strip adjacent to the appropriate number on spacing scale 43 and advancing the thermoplastic strip until that mark reaches the zero point. The second character is then cut in the same manner as previously described.

The first die 14 is removed from the die cooling station 150 by advancing the first die slightly until it projects from the exit end of the die cooling station from which it is then removed by hand. The second die 14 is then transferred to the die cooling station 150, and a new die 14 is inserted into the die heating station 12. These steps are repeated sequentially until the word or a series of words forming, for example,'a segment of a sign is completed. The thermoplastic strip 47 is then fed forward until the desired segment of the sign is completely available, and the same is then torn off against the tear-off bar at the exit end of the die cooling station 150.

To facilitate handling, an arrow or other indicia 192 (see FIG. 7) is formed on the back side of each die 14, as previously mentioned, to indicate the correct direc tion of insertion of the die into the sign forming apparatus. Either the positive or negative of the sign can be utilized by weeding inside or outside of the die cut letters and by transferring the resultant sign to a transfer tape by a suitable means, such as a suitable roller and applicator, after which the lettering may abe stripped from the paper release liner of the transfer tape and applied by its own adhesive to any appropriately prepared surface.

As previously described herein, the inter-character spacing is achieved by advancing the thermoplastic strip 47 by amounts equal to the appropriate sum of the half widths of the respective characters to be spaced and their appropriate average inter-character spacings, which half widths are given on the dies 14 normally located in the die cooling and heating stations 150 and 12 and are easily read from the mirrors 188 and 190. However, in the case of a particular combination of letters, as, for example, the letter W followed by the letter A, the intercharacter spacing may well be such that, with reference to a vertical line, the letters overlap when positioned for an eyepleasing appearance. In order to facilitate use of the present sign forming apparatus and to accommodate the freedom to space letters by eye, there is provided a template 198 (see FIG. 1) having indicia thereon corresponding to the more common letters requiring special spacing, such as the letters A, 0, L, T, and the like. The indicia on the template 198 are overprinted on each other on a single reference line, and the distance from the indicia to the right side of the template is equal to the distance from the center of the die in the die heating station 12 to the zero mark of the spacing scale 43, which serves as a fiducial mark for the accurate positioning of the thermoplastic strip 47. Thus, the operator may space letters by eye by moving the thermoplastic strip 47 backward until the last die cut letter appears and then positioning the template so that the next letter is in an eye-pleasing relationship to the preceeding letter. At that time, the operator marks the thermoplastic strip 47 at the right edge of the template and aligns that mark with the zero fiducial mark of the spacing scale 43 to bring the appropriate portion of the thermoplastic strip into aligned coincidence immediately under the character defined by the die 14 in the die heating station 12.

We claim:

I. In sign forming apparatus for reproducing characters or patterns in a strip of thermoplastic sheet material, a set of dies each having a planar configuration with a raised portion on one face conforming to a character or pattern to be reproduced, a die heating station including heating means for heating a die and further including means for slidably receiving and supporting the die with said one face thereof facing in a predetermined direction and with the opposite face thereof positioned adjacent to said heating means, a cutting pad for supporting the strip of thermoplastic sheet material opposite to said one face of a die supported by said die heating station, means for moving said die heating station between a first, ready position at which a die supported thereby is spaced away from said cutting pad anda second, cutting position at which the die supported thereby is positioned in engagement with said cutting pad to thereby cause the heated die to thermally cut the character or pattern defined on said one face thereof into the strip of thermoplastic sheet material interposed between the heated die and the cutting pad, and a die cooling station including means for slidably receiving, supporting, and cooling a heated die from said die heating station, said die cooling station being aligned to receive a heated die from said die heating station when the latter is in said first, ready position.

2. Sign forming apparatus as in claim 1 wherein each die comprises a flat plate of relatively thin cross section made of a high thermal-conductivity, low heat-capacity material, a raised bulb portion disposed on said plate and integrally joined thereto, said raised bulb portion linearly conforming to the outline of the character or pattern to be reproduced by the die and being rounded in cross section, a cutting bead formed on said raised bulb portion and defining an outline of the character or pattern to be reproduced by the die, said cutting bead being integrally formed with said raised bulb portion and symmetrically disposed on that side of said raised bulb portion away from said plate, said raised bulb portion serving as a heat sink for supplying heat to said cutting bead so that as said cutting bead is pressed into contact with the strip of thermoplastic sheet material said cutting bead is supplied with adequate heat to thermally cut through the thermoplastic material.

3. Sign forming apparatus as in claim 1 further including indicia means disposed on said opposite face of each die for indicating the correct direction of insertion of the die into the sign forming apparatus.

4. Sign forming apparatus as in claim 1 further including a spacing scale marked on the sign forming apparatus alongside the path of the strip of thermoplastic sheet material, and indicia means carried on each die for indicating its proper character half width and character spacing half width in the same values as said spacing scale.

5. Sign forming apparatus as in claim 1 further including a notch formed on one side of each die, and means forming a detent mechanism on said die heating station for engaging said notch whereby the position of a die can be felt by an operator when inserting a die into the sign forming apparatus.

6. ln sign forming apparatus, means forming a framework comprising a pair of side plates including upstanding portions, a base plate and means for connecting said base plate and said side plates into a selfsupporting structure, means, including a cutting pad carried on said base plate, forming a carrier plane for passing a thermoplastic material through the sign forming apparatus, means forming guide means vertically arranged between the upstanding portions of said side plates and interconnected therebetween, a die heating station carried on said guide means and including a heating plate, a heater and a thermostat for controlling the amount of heat supplied to said heating plate within a predetermined temperature range, and means secured to said heating plate for supporting said die heating station for sliding movement upwardly and downwardly on said guide means, means for moving said die heating station between a raised, ready position and a lower, cutting position in which a die carried on the underside of said heating plate is proximate said cutting pad and cuts through the thermoplastic material interposed between the die and said cutting pad, and a die cooling station including a heat sink having cooling fins thereon and further including fan means for moving air past said cooling fins to cool them, said die cooling station being mounted on said framework such that it is positioned to receive a die from said die heating station when the latter is in its raised, ready position.

7. Sign forming apparatus as in claim 6 wherein said means for moving said die heating station includes a cylindrical cam eccentrically mounted on said guide means, said die heating station includes first follower means disposed above said cam for raising said die heating station when a lobe defined by said cam is in an upper position, and second follower means is mounted below said cam for pressing said die heating station into thermal cutting relationship against the thermoplastic material when said cam is rotated to a lowermost position.

8. Sign forming apparatus as in claim 7 further including means for precisely adjusting the position of said second follower means to control the precise height of said die heating station in its lower, cutting position.

9. Sign forming apparatus as in claim 6 further including clamp rails positioned on each side of the thermoplastic material and overlying said cutting pad, means for normally urging said clamp rails into engagement with the edges of the thermoplastic material, and means associated with said clamp rails and said die heating station for disengaging said clamp rails from the thermoplastic material when said die heating station is in its raised, ready position.

10. In sign forming apparatus for reproducing characters or patterns in a strip of thermoplastic sheet material, a set of dies each having a planar configuration with a raised portion on one face conforming to the character or pattern to be reproduced and each being made of a material having a high thermal conductivity and a low total heat capacity so that it may be readily heated and cooled, a die heating station including die heating means for heating a die and further including means for slidably receiving and supporting the die with said one face thereof facing in a predetermined direction and with the opposite face thereof positioned adjacent to said die heating means, said die heating means being made of a material having a high thermal conductivity and a high total heat capacity so that its temperature is not markedly changed by heating a die applied thereto, a cutting pad for supporting the strip of thermoplastic sheet material opposite said one face of a die supported by said die heating station, means for moving said die heating station between a first, ready position spaced away from said cutting pad and a second, cutting position in engagement with said cutting pad thereby causing a heated die supported by said die heating station to thermally cut the character or pattern defined on said one face of the heated die into the strip of thermoplastic sheet material interposed between the heated die and said cutting pad, and a die cooling station including means for slidably receiving, supporting, and cooling a heated die from said die heating station, said die cooling station being aligned to receive the heated die from said die heating station when the latter is in said first, ready position.

11. In sign forming apparatus for fonning signs in a strip of thermoplastic sheet material by using a set of dies each of which has a planar configuration and a raised portion on one face thereof conforming to a character or pattern to be reproduced, a die heating station including means for slidably receiving, supporting, and heating a die with said one face thereof facing towards a cutting pad for supporting the strip of thermoplastic sheet material, means for moving said die heating station into engagement with said cutting pad to thereby cause a heated die supported by said die heating station to thermally cut the character or pattern defined on said one face thereof into the strip of thermoplastic sheet material interposed between the heated die and the cutting pad, and a die cooling station for receiving and cooling a heated die from said die heating station, said die cooling and heating stations including means for removing any die positioned in said die cooling station, remotely transferring any die positioned in said die heating station to said die cooling station, and feeding a die into said die heating station, whereby a plurality of dies may be successively employed to thermally cut the characters or patterns of a sign into the strip of thermoplastic sheet material by cooling each heated die immediately after it is employed to thermally cut a character or pattern of the sign while the next die is heated and employed to thermally cut the next character or pattern of the sign, said sign forming apparatus further including spacing means for aiding the operator to advance the strip of thermoplastic sheet material by an amount equal to the appropriate sum of the half widths of the characters or patterns defined on said one face of each of the dies in said die'heating and cooling stations and of the half widths of appropriate inter-character or pattern spacings for each of those characters or patterns to form a prespaced segment of a sign.

12. Sign forming apparatus as in claim 11 wherein said spacing means includes a fiducial mark on the sign forming apparatus, and a template having at least one indicium thereon corresponding to the next character or pattern to be thermally cut, whereby said template may be positioned over the strip of thermoplastic sheet material such that the indicium thereon is appropriately positioned relative to the preceding character or pattern thermally cut into the strip of thermoplastic sheet material, the strip of thermoplastic sheet material may then be marked to indicate the distance from said fiducial mark on the sign forming apparatus to the center of said cutting pad, and the strip of thermoplastic sheet material may then be advanced so that the mark thereon coincides with said fiducial mark.

13. Sign forming apparatus for forming characters in a strip of thermoplastic material, said apparatus comprising a die heating station for slidably receiving and heating a die having a planar base with a raised portion defining a character to be formed and facing the strip of thermoplastic material, a platen for supporting the strip of thermoplastic material opposite the raised portion of the die, means for moving the die heating station between a ready position spaced away from the platen to receive the die and a cutting position spaced closer to the platen to bring the die into contact with the strip of thermoplastic material and thermally die cut the character defined by the raised portion of the die in the strip of thermoplastic material, and a die cooling station for slidably receiving the die from the die heating station when the die heating station is in the ready position and for cooling the die.

14. Sign forming apparatus as in claim 13 wherein the planar base of the die comprises a flat plate of thinner cross section than the raised portion of the die, and the raised portion of the die comprises a bulb of rounded cross section integrally formed on this plate and a smaller cutting bead integrally formed on the bulb, the bulb serving as a heat sink for supplying the bead with adequate heat to thermally cut through the thermoplastic material.

15. Sign forming apparatus as in claim 13 wherein the die includes an indicium for indicating the correct direction of insertion of the die into the die heating station.

16. Sign forming apparatus as in claim 13 wherein a spacing scale is provided on the apparatus along the path of the strip of thermoplastic material, and an indicium is provided on the die to indicate the half width of the character defined thereon and a spacing therefor in the same units as the spacing scale.

17. Sign forming apparatus as in claim 13 wherein a notch is formed on one side of the die, and a detent mechanism is provided on the die heating station to engage this notch when the die is properly positioned in the die heating station.

18. Sign forming apparatus as in claim 13 wherein the die heating station includes a heating plate, a heater, and a thermostat for controlling the amount of heat supplied to the heating plate within a predetermined temperature range, and wherein the die cooling station includes a heat sink with cooling fins and a fan for moving air past these cooling fins to cool them.

19. Sign forming apparatus as in claim 18 wherein the heating plate is made of a material having a thermal conductivity and a total heat capacity such that its temperature is not markedly changed by heating a die applied thereto, and the die is made of a material having a thermal conductivity and a heat capacity such that it may be readily heated by the heating plate and cooled by the heat sink.

20. Sign forming apparatus as in claim 13 wherein the means for moving the die heating station includes an eccentrically-mounted cylindrical cam, and the die heating station includes first follower means disposed above the cam to raise the die heating station when a lobe of the cam is in an upper position and second follower means disposed below the cam to limit the downward stroke of the die heating station toward the strip of thermoplastic material supported on the platen and thereby determine the cutting position.

21. Sign forming apparatus as in claim 20 including means for precisely adjusting the position of the second follower means to adjust the cutting position of the die heating station.

22. Sign forming apparatus as in claim 13 including clamp rails overlying each side of the platen and the sheet of thermoplastic material supported thereon, means for normally urging the clamp rails into engagement with the edges of the strip of thermoplastic material, and means for disengaging the clamp rails from the strip of thermoplastic material when the die heating station is in the ready position.

23. Sign forming apparatus as in claim 13 wherein the die received by the die heating station is transferred to the die cooling station after the character defined by that die has been thermally die cut, another similar die is then fed to the die heating station, the strip of thermoplastic material is advanced by an amount equal to the sum of the half widths of the characters supported at the die cooling and heating stations and of the half widths of the desired spacing between each of those characters and its neighbor, the character defined by the die then supported at the die heating station is thereupon thermally die cut, and the foregoing steps are repeated to form a pre-spaced sign or a portion thereof.

24. Sign forming apparatus as in claim-l3 including a template having at least one i'ndicia thereon corresponding to the distance between the center of the next character to be formed, when the die 'on which that character is defined is at the die heating station, and a reference mark provided on the apparatus adjacent to the strip of thermoplastic material.

25. Sign forming apparatus as in claim 1 wherein the die comprises a plate of thermally conductive material, a raised bulb portion of rounded cross section integrally formed on this plate to indefine a character thereon, and a cutting bead of smaller cross section integrally and symmetrically formed on this bulb portion, the bulb portion serving as a heat sink for supplying the cutting bead with heat to thermally die cut through the sheet of thermoplastic material. 

1. In sign forming apparatus for reproducing characters or patterns in a strip of thermoplastic sheet material, a set of dies each having a planar configuration with a raised portion on one face conforming to a character or pattern to be reproduced, a die heating station including heating means for heating a die and further including means for slidably receiving and supporting the die with said one face thereof facing in a predetermined direction and with the opposite face thereof positioned adjacent to said heating means, a cutting pad for supporting the strip of thermoplastic sheet material opposite to said one face of a die supported by said die heating station, means for moving said die heating station between a first, ready position at which a die supported thereby is spaced away from said cutting pad and a second, cutting position at which the die supported thereby is positioned in engagement with said cutting pad to thereby cause the heated die to thermally cut the character or pattern defined on said one face thereof into the strip of thermoplastic sheet material interposed between the heated die and the cutting pad, and a die cooling station including means for slidably receiving, supporting, and cooling a heated die from said die heating station, said die cooling station being aligned to receive a heated die from said die heating station when the latter is in said first, ready position.
 2. Sign forming apparatus as in claim 1 wherein each die comprises a flat plate of relatively thin cross section made of a high thermal-conductivity, low heat-capacity material, a raised bulb portion disposed on said plate and integrally joined thereto, said raised bulb portion linearly conforming to the outline of the character or pattern to be reproduced by the die and being rounded in cross section, a cutting bead formed on said raised bulb portion and defining an outline of the character or pattern to be reproduced by the die, said cutting bead being integrally formed with said raised bulb portion and symmetrically disposed on that side of said raised bulb portion away from said plate, said raised bulb portion serving as a heat sink for supplying heat to said cutting bead so that as said cutting bead is pressed into contact with the strip of thermoplastic sheet material said cutting bead is supplied with adequate heat to thermally cut through the thermoplastic material.
 3. Sign forming apparatus as in claim 1 further including indicia means disposed on said opposite face of each die for indicating the correct direction of insertion of the die into the sign forming apparatus.
 4. Sign forming apparatus as in claim 1 further including a spacing scale marked on the sign forming apparatus alongside the path of the strip of thermoplastic sheet material, and indicia means carried on each die for indicating its proper character half width and character spacing half width in the same values as said spacing scale.
 5. Sign forming apparatus as in claim 1 further including a notch forMed on one side of each die, and means forming a detent mechanism on said die heating station for engaging said notch whereby the position of a die can be felt by an operator when inserting a die into the sign forming apparatus.
 6. In sign forming apparatus, means forming a framework comprising a pair of side plates including upstanding portions, a base plate and means for connecting said base plate and said side plates into a self-supporting structure, means, including a cutting pad carried on said base plate, forming a carrier plane for passing a thermoplastic material through the sign forming apparatus, means forming guide means vertically arranged between the upstanding portions of said side plates and interconnected therebetween, a die heating station carried on said guide means and including a heating plate, a heater and a thermostat for controlling the amount of heat supplied to said heating plate within a predetermined temperature range, and means secured to said heating plate for supporting said die heating station for sliding movement upwardly and downwardly on said guide means, means for moving said die heating station between a raised, ready position and a lower, cutting position in which a die carried on the underside of said heating plate is proximate said cutting pad and cuts through the thermoplastic material interposed between the die and said cutting pad, and a die cooling station including a heat sink having cooling fins thereon and further including fan means for moving air past said cooling fins to cool them, said die cooling station being mounted on said framework such that it is positioned to receive a die from said die heating station when the latter is in its raised, ready position.
 7. Sign forming apparatus as in claim 6 wherein said means for moving said die heating station includes a cylindrical cam eccentrically mounted on said guide means, said die heating station includes first follower means disposed above said cam for raising said die heating station when a lobe defined by said cam is in an upper position, and second follower means is mounted below said cam for pressing said die heating station into thermal cutting relationship against the thermoplastic material when said cam is rotated to a lowermost position.
 8. Sign forming apparatus as in claim 7 further including means for precisely adjusting the position of said second follower means to control the precise height of said die heating station in its lower, cutting position.
 9. Sign forming apparatus as in claim 6 further including clamp rails positioned on each side of the thermoplastic material and overlying said cutting pad, means for normally urging said clamp rails into engagement with the edges of the thermoplastic material, and means associated with said clamp rails and said die heating station for disengaging said clamp rails from the thermoplastic material when said die heating station is in its raised, ready position.
 10. In sign forming apparatus for reproducing characters or patterns in a strip of thermoplastic sheet material, a set of dies each having a planar configuration with a raised portion on one face conforming to the character or pattern to be reproduced and each being made of a material having a high thermal conductivity and a low total heat capacity so that it may be readily heated and cooled, a die heating station including die heating means for heating a die and further including means for slidably receiving and supporting the die with said one face thereof facing in a predetermined direction and with the opposite face thereof positioned adjacent to said die heating means, said die heating means being made of a material having a high thermal conductivity and a high total heat capacity so that its temperature is not markedly changed by heating a die applied thereto, a cutting pad for supporting the strip of thermoplastic sheet material opposite said one face of a die supported by said die heating station, means for moving said die heating station betwEen a first, ready position spaced away from said cutting pad and a second, cutting position in engagement with said cutting pad thereby causing a heated die supported by said die heating station to thermally cut the character or pattern defined on said one face of the heated die into the strip of thermoplastic sheet material interposed between the heated die and said cutting pad, and a die cooling station including means for slidably receiving, supporting, and cooling a heated die from said die heating station, said die cooling station being aligned to receive the heated die from said die heating station when the latter is in said first, ready position.
 11. In sign forming apparatus for forming signs in a strip of thermoplastic sheet material by using a set of dies each of which has a planar configuration and a raised portion on one face thereof conforming to a character or pattern to be reproduced, a die heating station including means for slidably receiving, supporting, and heating a die with said one face thereof facing towards a cutting pad for supporting the strip of thermoplastic sheet material, means for moving said die heating station into engagement with said cutting pad to thereby cause a heated die supported by said die heating station to thermally cut the character or pattern defined on said one face thereof into the strip of thermoplastic sheet material interposed between the heated die and the cutting pad, and a die cooling station for receiving and cooling a heated die from said die heating station, said die cooling and heating stations including means for removing any die positioned in said die cooling station, remotely transferring any die positioned in said die heating station to said die cooling station, and feeding a die into said die heating station, whereby a plurality of dies may be successively employed to thermally cut the characters or patterns of a sign into the strip of thermoplastic sheet material by cooling each heated die immediately after it is employed to thermally cut a character or pattern of the sign while the next die is heated and employed to thermally cut the next character or pattern of the sign, said sign forming apparatus further including spacing means for aiding the operator to advance the strip of thermoplastic sheet material by an amount equal to the appropriate sum of the half widths of the characters or patterns defined on said one face of each of the dies in said die heating and cooling stations and of the half widths of appropriate inter-character or pattern spacings for each of those characters or patterns to form a pre-spaced segment of a sign.
 12. Sign forming apparatus as in claim 11 wherein said spacing means includes a fiducial mark on the sign forming apparatus, and a template having at least one indicium thereon corresponding to the next character or pattern to be thermally cut, whereby said template may be positioned over the strip of thermoplastic sheet material such that the indicium thereon is appropriately positioned relative to the preceding character or pattern thermally cut into the strip of thermoplastic sheet material, the strip of thermoplastic sheet material may then be marked to indicate the distance from said fiducial mark on the sign forming apparatus to the center of said cutting pad, and the strip of thermoplastic sheet material may then be advanced so that the mark thereon coincides with said fiducial mark.
 13. Sign forming apparatus for forming characters in a strip of thermoplastic material, said apparatus comprising a die heating station for slidably receiving and heating a die having a planar base with a raised portion defining a character to be formed and facing the strip of thermoplastic material, a platen for supporting the strip of thermoplastic material opposite the raised portion of the die, means for moving the die heating station between a ready position spaced away from the platen to receive the die and a cutting position spaced closer to the platen to bring the die into contact with The strip of thermoplastic material and thermally die cut the character defined by the raised portion of the die in the strip of thermoplastic material, and a die cooling station for slidably receiving the die from the die heating station when the die heating station is in the ready position and for cooling the die.
 14. Sign forming apparatus as in claim 13 wherein the planar base of the die comprises a flat plate of thinner cross section than the raised portion of the die, and the raised portion of the die comprises a bulb of rounded cross section integrally formed on this plate and a smaller cutting bead integrally formed on the bulb, the bulb serving as a heat sink for supplying the bead with adequate heat to thermally cut through the thermoplastic material.
 15. Sign forming apparatus as in claim 13 wherein the die includes an indicium for indicating the correct direction of insertion of the die into the die heating station.
 16. Sign forming apparatus as in claim 13 wherein a spacing scale is provided on the apparatus along the path of the strip of thermoplastic material, and an indicium is provided on the die to indicate the half width of the character defined thereon and a spacing therefor in the same units as the spacing scale.
 17. Sign forming apparatus as in claim 13 wherein a notch is formed on one side of the die, and a detent mechanism is provided on the die heating station to engage this notch when the die is properly positioned in the die heating station.
 18. Sign forming apparatus as in claim 13 wherein the die heating station includes a heating plate, a heater, and a thermostat for controlling the amount of heat supplied to the heating plate within a predetermined temperature range, and wherein the die cooling station includes a heat sink with cooling fins and a fan for moving air past these cooling fins to cool them.
 19. Sign forming apparatus as in claim 18 wherein the heating plate is made of a material having a thermal conductivity and a total heat capacity such that its temperature is not markedly changed by heating a die applied thereto, and the die is made of a material having a thermal conductivity and a heat capacity such that it may be readily heated by the heating plate and cooled by the heat sink.
 20. Sign forming apparatus as in claim 13 wherein the means for moving the die heating station includes an eccentrically-mounted cylindrical cam, and the die heating station includes first follower means disposed above the cam to raise the die heating station when a lobe of the cam is in an upper position and second follower means disposed below the cam to limit the downward stroke of the die heating station toward the strip of thermoplastic material supported on the platen and thereby determine the cutting position.
 21. Sign forming apparatus as in claim 20 including means for precisely adjusting the position of the second follower means to adjust the cutting position of the die heating station.
 22. Sign forming apparatus as in claim 13 including clamp rails overlying each side of the platen and the sheet of thermoplastic material supported thereon, means for normally urging the clamp rails into engagement with the edges of the strip of thermoplastic material, and means for disengaging the clamp rails from the strip of thermoplastic material when the die heating station is in the ready position.
 23. Sign forming apparatus as in claim 13 wherein the die received by the die heating station is transferred to the die cooling station after the character defined by that die has been thermally die cut, another similar die is then fed to the die heating station, the strip of thermoplastic material is advanced by an amount equal to the sum of the half widths of the characters supported at the die cooling and heating stations and of the half widths of the desired spacing between each of those characters and its neighbor, the character defined by the die then supported at the die heating station is thereupon thermally die cut, and the foregoiNg steps are repeated to form a pre-spaced sign or a portion thereof.
 24. Sign forming apparatus as in claim 13 including a template having at least one indicia thereon corresponding to the distance between the center of the next character to be formed, when the die on which that character is defined is at the die heating station, and a reference mark provided on the apparatus adjacent to the strip of thermoplastic material.
 25. Sign forming apparatus as in claim 1 wherein the die comprises a plate of thermally conductive material, a raised bulb portion of rounded cross section integrally formed on this plate to indefine a character thereon, and a cutting bead of smaller cross section integrally and symmetrically formed on this bulb portion, the bulb portion serving as a heat sink for supplying the cutting bead with heat to thermally die cut through the sheet of thermoplastic material. 